Most useful ActionScript packages / libraries

Question

What are some useful plug-ins, packages or source-code for ActionScript?

Please include ActionScript version, name, link and description.

Answer 1

Things I'm actually using from time to time:

Degrafa: Degrafa is a declarative graphics framework open source licensed under MIT. (AS3)

FlexSpy: Visually inspect and tinker with display components. (Flex3)

AlivePDF: 100% client side PDF generation (AS3)

PureMVC: MVC framework (many platforms...)

Ravis Birdeye: Graph/Network visualization.

FlexLib: Extended controls.